DESCRIPTION

The ef_expand_file() function is part of the tecla library
(see the libtecla(3) man page). It expands a specified filename,
converting ~user/ and ~/ expressions at the start of the
filename to the corresponding home directories, replacing
$envvar with the value of the corresponding environment
variable, and then, if there are any wildcards, matching these against
existing filenames. Backslashes in the input filename are interpreted
as escaping any special meanings of the characters that follow them.
Only backslahes that are themselves preceded by backslashes are
preserved in the expanded filename.

In the presence of wildcards, the returned list of filenames only
includes the names of existing files which match the
wildcards. Otherwise, the original filename is returned after
expansion of tilde and dollar expressions, and the result is not
checked against existing files. This mimics the file-globbing behavior
of the unix tcsh shell.

The supported wildcards and their meanings are:

* - Match any sequence of zero or more characters.
? - Match any single character.
[chars] - Match any single character that appears in
'chars'. If 'chars' contains an expression of
the form a-b, then any character between a and
b, including a and b, matches. The '-'
character looses its special meaning as a
range specifier when it appears at the start
of the sequence of characters. The ']'
character also looses its significance as the
terminator of the range expression if it
appears immediately after the opening '[', at
which point it is treated one of the
characters of the range. If you want both '-'
and ']' to be part of the range, the '-'
should come first and the ']' second.
[^chars] - The same as [chars] except that it matches any
single character that doesn't appear in
'chars'.

Note that wildcards never match the initial dot in filenames that
start with '.'. The initial '.' must be explicitly specified in the
filename. This again mimics the globbing behavior of most unix shells,
and its rational is based in the fact that in unix, files with names
that start with '.' are usually hidden configuration files, which are
not listed by default by the ls command.

The following is a complete example of how to use the file expansion
function.

This function creates the resources used by the ef_expand_file()
function. In particular, it maintains the memory that is used to record the
array of matching filenames that is returned by ef_expand_file(). This
array is expanded as needed, so there is no built in limit to the number of
files that can be matched.

ExpandFile *del_ExpandFile(ExpandFile *ef)

This function deletes the resources that were returned by a previous call to
new_ExpandFile(). It always returns NULL (ie a deleted object). It
does nothing if the ef argument is NULL.

The ef_expand_file() function performs filename expansion, as documented
at the start of this section. Its first argument is a resource object returned
by new_ExpandFile(). A pointer to the start of the filename to be matched
is passed via the path argument. This must be a normal NUL
terminated string, but unless a length of -1 is passed in pathlen, only
the first pathlen characters will be used in the filename expansion. If
the length is specified as -1, the whole of the string will be
expanded.

The function returns a pointer to a container who's contents are the
results of the expansion. If there were no wildcards in the filename,
the nfile member will be 1, and the exists member should
be queried if it is important to know if the expanded file currently
exists or not. If there were wildcards, then the contained
files[] array will contain the names of the nfile existing
files that matched the wildcarded filename, and the exists
member will have the value 1. Note that the returned container belongs
to the specified ef object, and its contents will change on each
call, so if you need to retain the results of more than one call to
ef_expand_file(), you should either make a private copy of the
returned results, or create multiple file-expansion resource objects
via multiple calls to new_ExpandFile().

On error, NULL is returned, and an explanation of the error can
be determined by calling ef_last_error(ef).

const char *ef_last_error(ExpandFile *ef)

This function returns the message which describes the error that
occurred on the last call to ef_expand_file(), for the given
(ExpandFile *ef) resource object.

The ef_list_expansions() function provides a convenient way to
list the filename expansions returned by ef_expand_file(). Like
the unix ls command, it arranges the filenames into equal width
columns, each column having the width of the largest file. The number
of columns used is thus determined by the length of the longest
filename, and the specified terminal width. Beware that filenames that
are longer than the specified terminal width are printed without being
truncated, so output longer than the specified terminal width can
occur. The list is written to the stdio stream specified by the
fp argument.

THREAD SAFETY

In multi-threaded programs, you should use the libtecla_r.a
version of the library. This uses POSIX reentrant functions where
available (hence the _r suffix), and disables features that rely
on non-reentrant system functions. Currently there are no features
disabled in this module.

Using the libtecla_r.a version of the library, it is safe to use
the facilities of this module in multiple threads, provided that each
thread uses a separately allocated ExpandFile object. In other
words, if two threads want to do file expansion, they should each call
new_ExpandFile() to allocate their own file-expansion objects.